Valve surgery includes interventions where a cardiac valve is repaired, for instance with valve decalcification interventions or annuloplasty for atrioventricular valves. Alternatively, valve surgery may also involve interventions where the entire diseased valve is either replaced by a mechanical valve, a synthetic valve or bioprosthesis valve such as one derived from a porcine heart valve. The aortic or mitral valve is most commonly involved in valve surgery interventions.
Traditional valve surgery has been commonly performed through a midline sternotomy incision, where the patient's sternum is incised and the ribcage retracted to obtain access to the patient's heart and major blood vessels.
More recently, in minimally invasive procedures smaller parasternal incisions (mini-sternotomy) or intercostal thoracotomy approaches have also been employed. In thoracotomy approaches, two adjacent ribs are spread apart, at times even removing a length of rib to improve access into the patient's thorax and to the patient's heart. In both approaches, a chest retractor is used to spread apart the patient's skin and thoracic bone structure to maintain an incised opening or surgical window onto the underlying cardiac tissue.
Chest retractors exist in many sizes and shapes and have been present since the dawn of cardiac surgery. Most known chest retractors have an elongate rack bar and two retracting arms, namely a fixed retracting arm and a movable retracting arm. Both arms typically extend in a direction normal to the rack bar. The movable arm can be displaced along the rack bar, and relative to the fixed arm, by using a crank to activate a pinion mechanism which engages teeth on the rack bar. Two blades are provided, usually disposed below the retractor arm and extending into the surgical incision, to interface with the patient's skin and thoracic bone structure. These two blades apply the retraction that creates the surgical window by the relative movement and an ensuing spacing apart of the two retractor arms.
Traditional valve surgery has been performed with the support of a heart-lung machine, whereby the patient's blood is oxygenated outside the body through extracorporeal circulation (ECC) and the heart is arrested through administration of cardioplegia. This allows the surgeon to safely pierce and penetrate a heart chamber or a major heart vessel in order to perform a surgical intervention while the patient's blood flow is diverted and bypassed to the heart-lung machine. A series of cannulae and catheters are usually employed to divert the patients blood flow to the heart-lung machine for cardiopulmonary bypass and to return the oxygenated blood to the aorta. The aorta is cross clamped to avoid backflow into the heart chambers and surgical field. In aortic valve surgery, the aorta is cannulated for arterial return (aortic cannulation) usually at the pericardial reflection. Venous drainage is obtained by a cannula placed in the right atrial appendage (right atrial cannulation). A cannula serving to perfuse the arrested heart with cardioplegia solution during the surgical intervention is usually placed in the right atrium and directed into the coronary sinus (retrograde cardioplegia cannula). Mitral valve surgery has traditionally been performed with superior and inferior vena cavae cannulation (bicaval cannulation) and aortic cannulation. These cannulae and catheters are introduced into some cardiac tissue through the surgical window and tend to occupy the surgical workspace.
Subsequent to the creation of a surgical window through the patient's skin and thoracic bone structure, and following the placement of the patient on ECC, the great majority of valve surgery procedures involve some form of surgical incision of cardiac tissue and subsequent retraction of incised cardiac tissue to access the diseased heart valve. Cardiac tissue includes pericardium, epicardium, myocardium, endocardium, tissue of the septal wall, aorta tissue, vena cava tissue, cardiac valves, heart muscle, the coronary arteries and veins, the pleurae, the thymus, and other like anatomical tissue.
In traditional aortic valve surgery, surgical access to the diseased aortic valve is mostly achieved through a surgical incision in the aorta. An oblique incision (aortotomy) around a portion of the aorta's circumference is made in the segment of aorta between the aortic valve (AV) and the aortic surgical cross clamp (ACC). Alternatively, other like means of restricting backflow through the aorta, such as an intraluminal occluding balloon catheter, may also be used.
Following the aortotomy, three traction stay sutures (TSS) are usually placed through the commissures of the valvular annulus and suspended from surgical drapes under tension. A portion of these drapes is usually placed between the chest retractor blades and the patient's skin and bone structure along the sternotomy incision. Alternatively, the stay sutures may be anchored to the patient's surrounding cardiac tissue or to the chest retractor. In addition to stay sutures, a variety of hand held tissue retractors (HHR) are also deployed throughout the surgical intervention and used to help improve access to the aortic valve by displacing aortic tissue generally along the aortotomy incision (see FIG. 18). The valve annulus may then be carefully debrided of calcific deposits and, if required, the native valve is excised and replaced.
Surgical access to a diseased mitral valve (MV) is mostly achieved through a surgical incision of the left atrium. To attempt to achieve optimal exposure, the heart is elevated out of the chest and rotated, allowing the apex to drop posteriorly while elevating the right side of the heart. This maneuver tends to bring the posterior mitral valve leaflet towards the right side of the patient in a plane which tends to face the surgeon, often permitting better visualization of the mitral valve and subvalvular structures.
Following the median sternotomy, the pericardium is opened slightly to the right of the midline and the right side of the pericardium is sutured under tension to the chest wall to help provide the elevation of the right side of the heart. The pericardial edges on the left side of the incision are not suspended. After bicaval cannulation, the superior vena cava is usually mobilized by incising the pericardium above it. A tourniquet is often placed on the inferior vena cava and traction is applied in a general direction toward the patient's feet. This procedure further helps to elevate the right side of the patient's heart. The left atrium is generally incised parallel to the intra-atrial groove. This incision is usually extended below the superior vena cava and a considerable distance below the inferior vena cava.
Current known types of retractor systems for mitral valve surgery, usually with three tissue retractors each individually secured to a chest retractor, are used to maintain the exposure to the mitral valve through the left atrial incision (see FIGS. 19A and 19C). The operating table is usually also rotated away from the surgeon to improve visibility.
Due to the limitations of these current retractor systems, exposure of the mitral valve often requires additional maneuvers. Pledgetted stay sutures (PSS) may be placed through the mitral valve annulus at either commissure and traction exerted to help pull the mitral valve towards the surgeon.
Recently, with the advent of less invasive procedures, the mitral valve may also be accessed through a transeptal approach via the right atrium (see FIG. 20). After the aorta is cross clamped and cardiac arrest achieved with cardioplegia, the right atrium is incised first. Four traction stay sutures (TSS) are generally placed to keep right atrium open. The intra-atrial septum is subsequently incised to obtain access to the left atrium and the mitral valve. Typically, 2-3 pledgetted mattress sutures (PMS) are placed in the intra-atrial septum and traction is subsequently applied. This retracts the intra-atrial septum and enhances visualization of the mitral valve.
Hand held retractors (HHR) are engaged with the intra-atrial septum with an aim to improve exposure. Typically, at least two hand held retractors are used. One is placed in the superior portion of the left atrium along the intra-atrial septum incision, and pulled towards the patient's head or left shoulder. The other is placed in the inferior portion of the left atrium along the intra-atrial septum incision, and pulled towards the patient's feet or left foot. Tending to further facilitate exposure of the mitral valve, a Harrington retractor (HAR) is placed in the left atrium along the right side of the intra-atrial septum incision, and traction applied laterally towards the surgeon (i.e. towards the patient's right side). This often helps deliver the mitral valve into direct view of the surgeon. The surgical intervention on the mitral valve is at this point performed. The mitral valve mechanism is usually tackled first, after which a valvular annuloplasty is generally performed.
Current aortic and mitral valve surgeries described above may in some instances be characterized by a number of associated drawbacks as will be described in greater detail below.
The installation of traction stay sutures, used to retract cardiac tissue during valve surgery, may be a time-consuming process given the relatively high number of such sutures generally required and since the securing of said stay sutures through manual tying of the suture line is a multi-step threading and knotting procedure. Current mitral valve surgery may generally require 6-8 stay sutures; 4 current aortic valve surgeries may require 3-5 stay sutures.
The installation of traction stay sutures may at times be cumbersome given the limited space or poor access during the manual tie down of the suture line lengths, especially in surgical interventions where the surgical window is small.
Once the traction stay sutures have been placed, they are not conducive to allowing readjustment in either the retraction tensile load they apply on the cardiac tissue, or in the vector direction of the retraction load they apply. To readjust the retraction load or direction vector, the surgeon must untie and retie the suture line lengths or cut the existing suture line and replace it with a new suture that will be secured in a manner to exert the desired retraction load and direction vector on the cardiac tissue. Generally, adjustment of the desired tensile retraction by cutting an existing suture line and re-piercing a new suture line is not desirable. A re-piercing of the cardiac tissue with a subsequent suture tends to increase the likelihood of inducing tissue trauma or tissue tearing which may have to be surgically repaired.
At times, the vector direction of retraction that is achievable with stay sutures may be limited by the availability of anchoring points, or tie down points, for the stay suture. Anchoring points or tie down points, either in surrounding cardiac tissue or on the chest retractor, may not be present in a location that would enable the resultant traction direction to be the desired direction. Consequently, additional sutures are needed in order that a desired retraction direction vector is achieved by the sum of two or more stay sutures whose vector retraction directions yield a desired direction vector on the cardiac tissue.
Traction stay sutures tend to exert a concentrated load on the cardiac tissue. This may at times lead to tissue tearing. To redistribute these concentrated loads, pledgets are sometimes placed between the suture and the cardiac tissue in order to minimize the likelihood of tissue tearing. During removal of pledgetted traction stay sutures, it may be possible to unintentionally leave the pledget behind within the heart chamber which may lead to complications such as stroke or infarct if said pledget is not retrieved.
During aortic valve surgery, three traction stay sutures are usually installed, each one placed at the top of each commissure. This tends to result in a non-circular opening in the incised aorta perimeter which may interfere with the excision of the existing valve, or the sizing and installation of a new replacement valve. Consequently, hand held tissue retractors may also be deployed between two stay sutures, each engaged with aortic tissue, to attempt to render this opening more circular. In certain cases, these discrete concentrated loads from the traction sutures may tend to bend the aorta along its flow axis thereby distorting the aorta wall to collapse its diameter at the bend location, since there is insufficient support in tending to maintain the aorta circumference.
Valve replacement surgeries or annuloplasty surgeries are generally characterized by the high number of securing sutures placed through the valve annulus and either the annuloplasty ring annulus or the valve prosthesis annulus. As such, there tends to be an increased risk of suture tangling as the number of traction stay sutures required increases.
The use of hand held tissue retractors in valve surgery are also characterized by a number of associated drawbacks as will be described in greater detail below. Two to three hand held tissue retractors are typically used in current mitral valve surgeries and current aortic valve surgeries. Hand held tissue retractors must be held by the surgeon assistant or nurse. In addition to being a poor use of the surgeon assistant's time and abilities, hand held retractors make for an unstable surgical site since the retractors tend not to be kept still and motionless in the exact same position for extended periods of time. This may compromise the outcome of the surgery during delicate interventions which prefer a very stable surgical site.
Although available in a number of discrete sizes, hand held retractors are typically of fixed geometry. This tends to result in a compromised fixed tool configuration being employed on differing patient anatomies.
The use of chest-retractor-mounted tissue retractors in valve surgery is also characterized by a number of associated drawbacks, as will be described in greater detail below.
Current known retractor systems for mitral valve surgery performed through a left atrium approach may require as many as three chest-retractor-mounted tissue retractors (CRM). Tissue retractors generally consist of a tissue-engaging portion, blade or rake attached to a shaft which is secured to a chest retractor at the shaft free end. The high number of clamps and mounting rods associated with each of the three tissue retractors tends to make for a high part count and timely surgical set-up. Moreover, the high number of tissue retractors and associated mounting rods and clamps may, in certain instances, render the surgical space very cluttered and non-ergonomic.
Another limitation of some current valve surgery retractor systems is that the proximal shaft end of a tissue retractor is usually secured to the top of a chest retractor arm (FIG. 19C), or to a mounting rail substantially parallel to and slightly above a chest retractor arm (FIG. 19A). Consequently, the vector pull direction of an imposed retraction load on a cardiac tissue, which is generally substantially in line with the shaft axis of the tissue retractor, generally extends from the engaged cardiac tissue to a mounting point for the proximal shaft end of the tissue retractor on a chest retractor arm (or slightly above a chest retractor arm). The tops of the deployed chest retractor arms, which maintain a surgical window, generally form a substantially horizontal plane (when the patient is placed in a supine horizontal position on a surgical table). The farther an engaged cardiac tissue is from a deployed chest retractor arm where the proximal shaft end of the tissue retractor will be mounted, the more horizontal is the direction of the imposed tissue retraction load and of the tissue retractor shaft axis. The closer an engaged cardiac tissue is to a deployed chest retractor arm where the proximal shaft end of the tissue retractor will be mounted, the more vertical is the direction of the imposed tissue retraction load and of the tissue retractor shaft axis. Therefore, once the desired cardiac tissue is engaged by a tissue retractor, in some known current retractor systems the vector pull direction tends to be a resultant predetermined vector set by the mounting location of the proximal shaft end of the tissue retractor on the chest retractor. For instance, it may be very difficult to impose a vertical pull vector on an engaged cardiac tissue with some current valve surgery retractor systems. Furthermore, in some current known valve retractor systems, because the tissue-engaging portion, blade or rake is in a rigid fixed configuration relative to its tissue retractor shaft, and because the shaft is generally limited to being mounted to a chest retractor arm (or to a mounting rail parallel to and slightly above the chest retractor arm), the orientation of the tissue-engaging portion, blade or rake relative to its position within a surgical window is a substantially fixed result except for the free rotation of the tissue-engaging blade about the centerline of its shaft (if a round shaft is used). As a result, these current valve retractor systems may be able to place the tissue-engaging portion, blade or rake in many positions within a surgical window, but the orientation of the said portion at any such given position is greatly limited by the location on the chest retractor perimeter where the proximal shaft end is eventually mounted.
At times, in order to provide the desired traction vector on a cardiac tissue, the proximal shaft end of the tissue retractor must be secured in a location too far away from a mounting clamp available on the chest retractor. Bringing the proximal shaft end to the location of the mounting clamp available on the chest retractor where it can subsequently be secured, may result in a compromised traction vector. Consequently, one or more additional co-operating tissue retractors must also be deployed such that the desired traction vector is obtained through the vector sum of the additional tissue retractor traction vector and the initial compromised traction vector. This tends to lead to more parts required to achieve the desired tissue retraction and consequently a more cluttered surgical workspace.
In process re-adjustments of the tissue retractors in some known valve surgery systems may at times prove fastidious. For example, in a typical mitral valve surgery set-up with a known valve retractor system, two tissue retractors are generally mounted on a left chest retractor arm to retract cardiac tissue towards the left side of a patient. Another tissue retractor is mounted of an extension rod to retract cardiac tissue towards a patient's feet (see FIG. 18A). The extension rod is also mounted to the left chest retractor arm in a substantially perpendicular and generally horizontal orientation. If the surgeon wants to change the orientation of the tissue-engaging portion of the middle tissue retractor, for instance, the mounting clamp of the middle tissue retractor must be repositioned along the left chest retractor arm. Larger re-orientations generally require more translation of the mounting clamp along a chest retractor arm (or along a mounting rail substantially parallel to and slightly above a chest retractor arm). In certain cases, the re-orientation required is sufficiently great that the mounting clamp of the middle tissue retractor must be translated considerably along a chest retractor arm (or along its mounting rail) that it may interfere with the mounting clamp of an adjacent tissue retractor. This may lead to a major take down of the surgical set-up.
Some known tissue retractors are constructed with a number of rod-like extensions assembled in a rake-like arrangement to configure a tissue-engaging portion (see FIG. 18B). This may lead to concentrated loads exerted on an engaged cardiac tissue by the rod contact surfaces, and consequently be more prone to induce tissue trauma.
Some current retractor systems for valve surgery are comprised of a number of similar tissue retractors. These tissue retractors are generally of a fixed rigid geometry and design.
In some known retractor systems for valve surgery, the proximal shaft end of the tissue retractor must first be inserted and engaged within its mounting clamp before the tissue-engaging portion or blade may be placed into contact with the cardiac tissue. This may compromise the approach vector of a tissue retractor to a cardiac tissue desired to be retracted.
In minimally invasive valve surgery, the size of the surgical incision and the size of a retracted surgical window are considerably reduced. Vacuum-assisted venous drainage has been developed to reduce the size of venous cannulae used in cardiopulmonary bypass. The smaller sizes of these cannulae tend to prevent them from being an obstacle to the surgical procedure. However, the number of traction sutures and number of tissue retractors, either hand held or chest-retractor-mounted, still used in current approaches tends to be obstructive in certain cases, given the smaller surgical window.
Thus it is a first object of the present invention to provide a surgery tool tending to alleviate the above mentioned drawbacks.
It is another object of the present invention to aim to improve the exposure and access to the diseased cardiac valve by providing a valve surgery tool that tends to minimize the number of traction stay sutures, hand-held tissue retractors, or chest-retractor-mounted tissue retractors used in current valve surgery interventions.